We have 300 million humans, each producing 3-4 pounds of waste/day. We also have several hundred million domestic animals (cattle, pigs, sheep, horses) also contributing.
If all of this waste could be collected and fermented, how much methane could be produced?
Would it be significant in terms of or energy use?
As I understand it, biogas is essentially newly-created natural gas, so couldn’t it be compressed and dumped into the existing NG pipeline ystem?
To guess, probably less than half of the energy that was spent in collecting it.
The key part of your question is “If all of this waste could be collected”. And the answer is it can’t. Not economically.
Absolutely spot on. The companies looking to do this sort of fermentation are looking at wastes that are already being collected for some other purpose to justify the costs of collection. (People are looking at how to ferment the same grains/waste/biomass twice in order to maximize the yield as this is cheaper than bringing in new or additional material.
It looks like you are looking primarily at “defecant” with your definition of waste, but this is very poor yield as it has already been processed by organisms to provide energy etc. Most people talk about biomass waste as being residue, or leftovers, from crop harvesting like stalks, cobbs, leaves. As such I can’ find any numbers for amount of defecant and efficiency for conversion to other materials/energy.
For some very beginning understanding of the problem:
Energy use The second plot is the industry standard from the DoE on U.S. energy flow.
Mahaloth’s thread from last year is the top Google hit But doesn’t answer the question either. I think people immediately give up on human waste for fuel and have never done the calculations.
I don’t understand-most US cities have sewage systems, and the waste is sent to a processing plant. So it is being collected now-why not use it to make methane?
Seems like a lot of shit going to waste!
Those plants almost all have a treatment plan that already makes use of this waste. Replacing that with a new system to produce biogas from this waste is not likely to be economical (even thoughf a new system might be more efficient). In particular, biogas requires fermentation, which takes time – so you would need a large storage area for this to take place. Many of these plants are in or near big cities, without spare space for such a storage area.
Here in the Minneapolis-St. Paul area, it goes to the sewage treatment plant at Pigs Eye, where the ‘solids’ are burned (and energy recovered from that) and then the remaining ashes are sold to local farmers and used as fertilizer on their fields. So not much is going to waste! I think most large treatment plants are similarly set up to make use of this waste.
Am I the only one who, when reading the subject line, wondered what a “Bioga” was? And why we need to produce more of them?
J.
Nope. Save the Biogas!
No, you’re not.
Same here.